Baffin Bay is an Arctic marginal sea connected to the North Atlantic via Davis Strait and the Labrador Sea. While the exchange of heat and freshwater through Davis Strait is known to strongly influence the subpolar North Atlantic, there are significant gaps in our understanding of the circulation and water mass distribution and transformation throughout Baffin Bay, in part due to limited direct velocity observations. In this study, high-resolution hydrographic, nutrient, oxygen isotope, and velocity data from two shipboard surveys in late-summer to early-fall 2021 are used to address these gaps. During the time period of observation, Baffin Bay was dominated by cold, fresh, nitrate-depleted Polar Water (PW) in the upper 300 m, with the coldest and freshest PW distributed along the western shelf and slope adjacent to Baffin Island. Only a small amount of warm and salty Atlantic-origin water was measured entering the southeastern bay at depth, which is diluted rapidly when passing through Davis Strait. Pacific-origin freshwater was dominant in the upper 200 m on the western side, with relatively small amounts of meteoric water on both sides of the bay. The circulation in Baffin Bay was generally cyclonic, consisting of a strong, surface-intensified western boundary current and a slower, weakly baroclinic eastern boundary current. Much of the eastern boundary current bifurcated to the west at the northern end of the Labrador Sea, and, as the remaining flow progressed through Davis Strait, it transitioned from surface-intensified to bottom-intensified. Basin-scale recirculation of the PW was documented using the shipboard data, which was also evident in the velocity field of an ocean reanalysis product for the same time period. Examination of the reanalysis fields from 1993 to 2021 indicates that the circulation in Baffin Bay was anomalously cyclonic during summer/fall 2021. Such basin-scale circulation anomalies can arise due to both the local wind stress curl pattern and remote wind forcing associated with the Arctic Oscillation index.

中文翻译：

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巴芬湾的水团演变和总体环流：2021 年两次船上调查的观察结果


巴芬湾是北极边缘海，通过戴维斯海峡和拉布拉多海与北大西洋相连。虽然已知通过戴维斯海峡的热和淡水交换对北大西洋的亚极地有很大影响，但我们对整个巴芬湾的环流和水团分布和转变的理解存在重大差距，部分原因是直接速度观测有限。在这项研究中，来自 2021 年夏末秋初两次船上调查的高分辨率水文、营养、氧同位素和速度数据用于解决这些差距。在观测期间，巴芬湾上部 300 m 以寒冷、新鲜、硝酸盐含量低的极地水 （PW） 为主，最冷和最新鲜的极地水分布在靠近巴芬岛的西部大陆架和斜坡上。仅测量到少量来自大西洋的暖咸水在深处进入东南湾，这些水在通过戴维斯海峡时被迅速稀释。太平洋起源的淡水在西侧的上部 200 m 占主导地位，海湾两侧的流星水相对较少。巴芬湾的环流通常是气旋性的，由一个强大的、表面增强的西部边界流和一个较慢的、弱斜压的东部边界流组成。东部边界流的大部分在拉布拉多海北端向西分叉，随着剩余的流流通过戴维斯海峡，它从表面增强过渡到底部增强。使用船上数据记录了 PW 的流域尺度再循环，这在同一时期的海洋再分析产品的速度场中也很明显。 对 1993 年至 2021 年再分析场的检查表明，巴芬湾的环流在 2021 年夏季/秋季是异常的气旋。这种流域尺度的环流异常可能是由于与北极涛动指数相关的局部风应力旋曲模式和远程风强迫而出现的。